How Cruise Control Systems Work

The cruise control system actually has a lot of functions other than controlling the speed of your car. For instance, the cruise control pictured below can accelerate or decelerate the car by 1 mph with the tap of a button. Hit the button five times to go 5 mph faster. There are also several important safety features -- the cruise control will disengage as soon as you hit the brake pedal, and it won't engage at speeds less than 25 mph (40 kph).

The system pictured below has five buttons: On, Off, Set/Accel, Resume and Coast. It also has a sixth control -- the brake pedal, and if your car has a manual transmission the clutch pedal is also hooked up to the cruise control.

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The on and off buttons don't actually do much. Hitting the on button does not do anything except tell the car that you might be hitting another button soon. The off button turns the cruise control off even if it is engaged. Some cruise controls don't have these buttons; instead, they turn off when the driver hits the brakes, and turn on when the driver hits the set button.

The set/accel button tells the car to maintain the speed you are currently driving. If you hit the set button at 45 mph, the car will maintain your speed at 45 mph. Holding down the set/accel button will make the car accelerate; and on this car, tapping it once will make the car go 1 mph faster.

If you recently disengaged the cruise control by hitting the brake pedal, hitting the resume button will command the car to accelerate back to the most recent speed setting.

Holding down the coast button will cause the car to decelerate, just as if you took your foot completely off the gas. On this car, tapping the coast button once will cause the car to slow down by 1 mph.

The brake pedal and clutch pedal each have a switch that disengages the cruise control as soon as the pedal is pressed, so you can shut off the cruise control with a light tap on the brake or clutch.